Pre-impregnated (pre-preg) material is used in the formation of high-strength low weight structures, such as, but not limited to, parts used to build aircraft and spacecraft. Pre-preg material is typically made-up of a composite of reinforcing fibers (such as carbon, glass, aramid, and the like) that are bonded together with a resin system. Pre-preg material is typically manufactured in flat sheets that are applied in multiple fiber orientation layers onto surfaces of a tool to form the shape of a desired part. The laminate is subsequently compacted and heat set (cured or fused) into a composite structure. Other methods of hardening or curing the laminate can also be used with some resins including, but not limited to, electron beam cure, microwave cure and ultraviolet light cure. There are various pre-preg materials fiber architectures that include, but are not limited to, woven fabric, unidirectional tape (uni-tape), non-crimp stitched broadgoods, braid, multi-dimensional weave, stretch broken fibers, and strategically stitched materials. A wide variety of resins can be used including, but not limited to, room temperature set resins, thermoset resins, and thermoplastic resins. The application of pre-preg material on tools, which have forming surfaces with at least two different radii of curvature, can be difficult to accomplish without wrinkling the material, folding the material, or requiring the fibers to be cut (darting the material to conform without creating folds or wrinkles); all of which generally reduces structural properties and functionality of the structure.
For the reasons stated above and for other reasons stated below that will become apparent to those skilled in the art upon reading and understanding the present specification, there is a need in the art for a method of conditioning or stretch-forming pre-preg material for effective and efficient application to forming surfaces of a tool having at least two different radii of curvature.